title: Infrared spectra of cyanoacetaldehyde (NCCH2CHO): a potential prebiotic compound of astrochemical interest.
abstract: Cyanoacetaldehyde (NC-CH2CH=O) and its isomer, cyanovinylalcohol (NC-CH=CH-OH), as possible components of the interstellar medium, comets, or planetary atmospheres, exist in equilibrium in the gas phase, although the latter compound is very much in the minority (2%). The recording and analysis of the gas-phase infrared spectrum of the former compound within the 4000-500 cm(-1) spectroscopic range and the potential presence of the latter isomer, which could be vital for their detection in these media, are reported. CCSD(T) and G4 high-level ab initio methods, as well as density functional theory calculations, predict the existence of two stable rotamers of cyanoacetaldehyde. The global minimum has a structure with an unusual O-C-C-C dihedral angle (150°) that falls between the antiperiplanar (180°) and anticlinal forms (120°). The second rotamer, which is about 4.0 kJ mol(-1) less stable in terms of free energy, has a planar structure that corresponds to the synperiplanar form (O-C-C-C dihedral angle: 0°). The absorption vibrational bands of the two aldehyde rotamers that are present in the mixture lead to a spectrum with a very complex structure in the region of deformation movements, in which several low-intensity bands overlap. A complete and unambiguous assignment of the experimental spectrum has been achieved by using the calculated harmonic and anharmonic vibrational frequencies.
authors.affiliation: Institut de Physique de Rennes, CNRS UMR 6251, Université de Rennes 1, 35042 Rennes, France. benidar@univ-rennes1.fr
authors.forename: Abdessamad
authors.initials: A
authors.lastname: Benidar
authors.forename: Robert
authors.initials: R
authors.lastname: Georges
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Guillemin
authors.forename: Otilia
authors.initials: O
authors.lastname: Mó
authors.forename: Manuel
authors.initials: M
authors.lastname: Yáñez
keywords: IR spectroscopy; ab initio calculations; astrochemistry; cyanoacetaldehyde; density functional calculations